There is provided a method for obtaining a high-purity alkyladamantyl ester from an alkyladamantyl ester composition containing a large quantity of alkyladamantyl halide obtained by, for example, alkylating raw material 2-adamantanone obtained through oxidation of adamantane by use of an organic metal reagent and then causing an acid halide to react with the resulting product, efficiently by a simple process. To an alkyladamantyl ester composition containing an alkyladamantyl halide such as 2-chloro-2-methyladamantane in an amount of larger than 0.5 parts by weight based on 100 parts by weight of alkyladamantyl ester such as 2-methyl-2-adamantyl methacrylate, a mixed solution of, for example, methanol and a sodium hydroxide aqueous solution is added. By bringing the alkali compound into contact with the alkyladamantyl halide in a homogeneous system so as to convert the halide into a compound which produces no acid when heated, the amount of the alkyladamantyl halide in the composition is reduced to 0.5 parts by weight or less based on 100 parts by weight of the alkyladamantyl ester, after which distillation is carried out.